Familial hypertrophic cardiomyopathy is a genetically heterogeneous disease with variable clinical features that is inherited as autosomal dominant with variable penetrance. Recent developments in genetics of hereditary cardiomyopathy have not only enlightened many points about pathogenesis, but have also provided great benefit to diagnostic approaches of clinicians. Heterozygous mutation of c3691-3692insTTCA in MYBPC3 gene was identified in a pediatric patient with diagnosis of hypertrophic cardiomyopathy at clinic. Hypertrophy was observed in sister and father of the patient in echocardiography screening, and it was subsequently determined that they also had same mutation. This mutation has not previously been defined and reported previously in the literature as cause of hypertrophic cardiomyopathy.